The bar code, which is one-dimensional code information as a purpose of merchandise management, inventory management or the like, and the two-dimensional code as a code having any higher information density have been known. A method has been known such that the code information is imaged by a solid-state image sensing device such as CMOS image sensor and CCD image sensor, as a device for imaging the two-dimensional code, various kinds of processing are performed on an image thereof, and it is binarized and decoded.
The CMOS image sensor used in such an apparatus which reads the code information has not been different from the one equipped for a digital camera or the like in a function so that it is required to have also a function as a camera to normally take photographs of an object and/or a scene. For example, in a case of the inventory management, it is used in a case where a target article and a location in which the article is stored are imaged, which are stored in a database together with any code information.
A small-scaled camera using the above-mentioned CMOS image sensor is equipped for a mobile phone. The camera function of the most of mobile phones includes a scanner for barcode/two-dimensional code and an optical character reader (OCR) other than that of taking a photograph of a scene or a person like the normal digital cameras. Namely, a digital camera, which is provided with any code-symbol-photographing-and-decoding function, has been widely needed (see, for example, Patent Document 1).
Further, in a field of the above-mentioned merchandise management, inventory management or the like, it is necessary to scan code symbols applied to articles one after another. In this moment, it is desirable to equip with an autofocus function, and the autofocus function and an imaging process are required to be fast.
Generally, a method is considerably used such that lens is arranged so as to move along an optical axis thereof, a distance on which it is in focus on the code symbol is calculated, and the lens moves up to a position that is suitable for the distance (see, for example, Patent Document 2). Further, a simple autofocus is considerably used such that two lens locations of short and long ranges, in addition to a fixed lens location, are stored in a memory and when failing to image, the lens moves to a direction of the short range or the long range (see, for example, Patent Document 3).
Additionally, as a more efficient method, a method using a liquid lens has been realized (see, for example, Patent Document 4). The liquid lens is configured so as to contain water solution having high conductivity and oily fluid having insulation in a container through which light is permeable. The water solution and the oily fluid are not mixed and have a boundary surface. Electrodes are provided at both ends of the container and by applying voltage on the electrodes, it is possible to change a shape of the boundary surface between the water solution and the oily fluid from a flat shape to a convex or concave shape using electro-wetting phenomenon.
Such an operation enables a flexural rate of the lens to alter to implement any focus control. It is called as varifocal lens because the focus control is implemented in the lens, not driving the lens mechanically.
The varifocal lens is very suitable for an apparatus such as a cord scanner or a mobile phone, in which an imaging function area is small, because any mechanically driving area is not necessary.